For pizza-events, be able to choose from multiple lists of food.
Some day, we might want to order other food rather than pizzas every time (GM's for example). In that case, it would be very nice to be able to use pizza.thalia.nu (which might needs the alias order.thalia.nu then).
In the backend, one should be able to enter multiple lists with items ('pizzas'). For each pizza-event, one should choose which list to use. This way we could have a list 'Dominos' and a different list 'Cafetaria Heyendaal' for example.